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递归与组合
作者:武汉SEO闵涛  文章来源:敏韬网  点击数710  更新时间:2009/4/23 18:59:19  文章录入:mintao  责任编辑:mintao

       福利彩票和体育彩票近两年比较火暴,相应在VB论坛上大家讨论也较多。其实选择彩票与集合选择子集相同道理。下面给出一种VB的递归算法(虽然明知存入数组会加快运算速度,但最终也没能满意地实现,请大家多多指教。另外,效率确实不高)
Option Explicit

Private Sub Command1_Click()

Dim temp, i As Long, starttime As Long, endtime As Long
starttime = Timer
temp = cmn(22, 6)
endtime = Timer
Open "d:\mofn.txt" For Binary As #1 ''''写入文件
Put #1, , temp
Close #1

MsgBox UBound(Split(temp, vbCrLf)) + 1 & " 种组合", 64, "共用时 " & endtime - starttime & " 秒" ''''计算组合可能情况和耗时

End Sub

 


Function cmn(ByVal m As Integer, ByVal n As Integer) As String '''' select n number from 1~m
Dim a() As String, temp As String, i As Long

ReDim a(1 To m) ''''定义数组
For i = 1 To m
a(i) = i
Next


If m = 3 Then
If n = 1 Then cmn = 1 & vbCrLf & 2 & vbCrLf & 3
If n = 2 Then cmn = "1,2" & vbCrLf & "1,3" & vbCrLf & "2,3"
If n = 3 Then cmn = "1,2,3"

ElseIf m > 3 Then
If n = 1 Then cmn = Join(a, vbCrLf)
If n = m Then cmn = Join(a, ",")
If n > 1 And n < m Then
temp = cmn(m - 1, n - 1)
''''Debug.Print m - 1 & "," & n - 1 & vbCrLf & "----------------" & vbCrLf & temp & vbCrLf & "---------------------------" & vbCrLf ''''可以在立即窗口查看算法过程
temp = Replace(temp, vbCrLf, "," & m & vbCrLf) & "," & m
cmn = cmn(m - 1, n) & vbCrLf & temp
End If

End If

End Function

 

下面给出利用集合实现不重复随机选取某几个号码,这个函数也可用来实现数组全部元素的随机排列。

Function getone(ByVal m As Integer, ByVal n As Integer) As String '''' one random option to select n number from 1~m without repeat number
Dim a() As String, temp As New Collection, i As Long, tempi As Long

ReDim a(1 To n) ''''定义数组
For i = 1 To m
temp.Add i   ''''可以根据需要更改

Next


Randomize
For i = 1 To n
tempi = Int(Rnd * temp.Count) + 1
a(i) = temp(tempi)
temp.Remove tempi
Next
getone = Join(a, ",")
Set temp = Nothing
Erase a
End Function

Private Sub Command2_Click()''''演示用法
MsgBox getone(30, 8), 64, "30选8 的一种选法"
MsgBox getone(100, 100), 64, "1 到100 的一种不重复全排列"
End Sub

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